Heetey dbeyfus



H. DREYFUS.

MANUFACTURE 0F ACETIC ALDEHYDE.

' APPLICATION FILED JUNE 1.*19517.

Patented July 22, 1919.

BY HIS ATTORNEYS B'ENRY DREYFUS, OF BASEL, SWITZERLAND.

MANUFACTUR OF ACETIC ALDEHYDE.

To all whom #may conc-ern:

Be it.known that I, HNRY DREYFUS, of

Basel, Switzerland, have invented certain new and useful Improvements in or Relating to the Manufacture. of Actetic Aldehyde, of which the following is a specication.

This invention relates to the manufacture of acetaldehyde from acetylene by passage` ofacetylene into an absorbing solution con tainling amercury compound and -sulfuric acid.

The manufacture of acetic aldehyde is of particular importance in view of its employment for transformation into acetic acid.

This manufacture of acetic acid is only interestmg industrlally if the acid can be produced at a low price which can compete with the processes hitherto employed, such as the acetate of lime process. The problem .of manufacturing acetaldehyde by processes of the character indicated is very difiicult, both as regards providing a process capable of producing actcladehyde economically on a large scale, and asl regardsproviding ap aratus which will allow of such -a manu aC.- ture.

The chlief difliculty in regard to apparatus is due to the employment of mercury or its salts or compounds, as these amalgamate with all metals except iron, so that these metals cannot be used. Iron itself cannot be used for the apparatus, owing to the employment of acids in the process, which at- (Serial No. 229,174, filed April. 17,1918,

being a division hereof) of providing apparatus ermitting of the industrial realization o the process.

The new process will be first described Specification of Letters Patent. Patented July 22, 1919,

Application led June 1, 1917. Serial No. 172,3215.

and the apparatus to be employed will be described vfurther on.

The process of manufactura-The aim of my present process of manufacture is to produce per kilo of mercury salt or compound employed in one operation before recovery of the mercury, the greatest possible amount of aceticaldehyde and without the production of crotonic aldehyde or other condensation products which have no valu@ for the manufacture of acetic aldehyde.

The question of whether the yield of acetic aldehyde based upon the quantity of acetylene introduced approaches lthe theoretical is a matter of secondary importance as compared with the question of whether a given amount of mercurial catalyst can be made to produce a large yield of aceticaldehyde beforel 1t becomes exhausted.

introduced, and the quantity of acetic aldehyde obtained werelonly the same as or even double the quantity of oxidof mercury or lsalt of mercury employed, this result would not be of commercial interest. l With the present invention one can obtain yields of acetic aldehyde t amounting in weight to from live to ten or more times the weight of-the mercury compound employed, or even fifteen to twenty times this weight.

The result in view is only obtained by observing a large number of conditions, all

of which must be followed', for each of them Aassists in obtaining a large yield such as above indicated.

These conditions are as follows;- (I). The amount of sulfuric acid used must be betweenabout 10% and about 15%, of the weight' of the absorbing solution. This amount provides for the presence of free sulfuric acid in the solution.

(II). The oxid or other compound of mer- Acury compound in the absorption liquid has become gray or grayish black, which indicates that the solution has reached about its maximum absorbing power, the acetylene being then introduced as rapidly as possible, While avoiding excess and non-absorption.

(V). Strong agitationis maintained during the introduction of the acetylene, so as to secure intimate mixture thereof with the absorption liquid.

(VI) The acetald'ehyde formed is distilled offat intervals by raising the temperature, but not above about 5060 C., the temperature being reduced to the lower temperature set forth under (III) for the reintroduction ofthe acetylene, Athe operations of-acetaldehyde production and distillation being repeated in alternation, as manytimes as required.

The acetylene is preferably introduced under a super-atmospheric pressure of about 'half an atmosphere. 1

'When the absorbing power of the solution has dlminished considerably or ceased in the course of the repeated absorptions and Adistillations, the solution may beV heated above 60 C. to vdistil off remaining traces of acetaldehyde.

The oxid or compound of mercury employed should be entirely dissolved in the is formed, because this would prevent the v absorption liquid before introducing the acetylene. This may be effected by heating the liquid-containing the mercury compound to dissolve the same, `the liquid being then cooled to the appropriate temperature for the introduction-of the acetylene.

The acetylene should be freed from its impurities, such as sulfureted. hydrogen,

` phosphoreted'hydrogen, or ammonia, before .introduction into the solution.

It must not be'attempted to convertv the acetaldehyde Vinto acetic acid by simultaneous oxldatlon with an' oxidizingagent as it reduction of themercury compound to the active form. referred to, and the increase of the concentration, of, the acid, as acetic acid was formed, would disturb the equilibrium in the conditions necessary to `arrive at the industrial result.

The hydration of acetylene by'sulfuric acid was studied by Berthelot (see for eX- ample Annales ale Chimie et de Physique richte Vol. XVII page 13) as applied to process consisting in forming a compound of the acetylene with bichlorid, sulfate or acetate of mercury' and decomposing the resulting productl with watell (Annales de Chimie et de Physique VI. Vol. 15 page Erdmann and Kthner effected the manufacture of acetic aldehyde from acetylene in 1898 (Zeitschrift fr Anorganische 0hemie,.85 Vol. 18, 1898, page 55) by passing a current of acetylene through a heated liquid containing oxid of mercury and about 40 per cent. of sulfuric acid. In working according to this process the intensiveabsorption of the acetylene causes much acetic aldehyde to distil, while another part of the acetylene introduced is transformed linto condensation products such as crotonic aldehyde, etc. During'the introduction, the liquid, after a certain time, becomes colored moreA and more, and at length becomes quite dark, and little by little the absorption of the acetylene diminishes, and finally ceases altogether. In view of this fact, others have employed the same liquid containing oXid of mercury with 45 per cent. of sulfuric acid, at lower temperatures,` below 50 C. and es ecially 15 4to 30 C., but vthe result is-unsatisfactory on account of the very great condensing action of the sulfuric acid of 45%, which forms at once crotonic aldehyde and resins, and because of the cessation of the absorption.

French Patent No. 474,246y of 29 June 1914 uses a high temperature of 50 to 70 110 C. with a high concentration of theacid, to cause the acetic aldehyde formed to escape the condensation.

According to French Patent No. 360249 of 17 February 1905 only a restricted quan- 115 tity of acetic aldehyde is obtained. Like- Wise in the Berichte 42 (2)4 1909 page 27 59 Kutcherow has described a process analogous to his previous process, employing zinc and cadmium salts instead of mercury comcent. in acid, (according to the example page 2 even 3% per cent. of acid), just about sufficien-t to convert the oxid of mercury into sulfate 'of mercury.

In that process i-t is intended for the aldelow 40 C. .during the introduction and absorption of the acetylene, and the percentage of total sulfuric acid in the solution is not less than 10 per cent. and not more than 15 per cent., the best absorption and yield being obtained between'afbout 25 or 30 and 40 C. At substantially lhigher temperatures such as indicated in the English Patent 6000/1913 the acetaldehyde-producing power of the oxid lor compound of mercury is much less, the acetylene thenA` acting materially to render. the mercury. compound more inac'tive'for the absorption of acetylene, and forming-mercurial condensation products, probably carbids of mercury, polymeriz'ed and inactive. On the other hand the limits of 10 Iand 15 per cent. total sulfurie acid are observed in the present invention. I have found in fact that in employing .free sulfuric -acid in the solution, the amount .of free sulfuric -acid 'being however, as an important. principle, Within certain 'low limits, one can vattain not only live times the weight in acetaldehyde of the weight of the oxid of mercury employed, but

8 to 10 times or l5 to 20 times as much asv the weight :of the oxid of mercury or salt of mercuryemployed, and on the other hand l have found that if sulfuric acid is only used in a quantity such that itis just suiiicient to make the sulfate of mercury, the yield is much less, but that the yield will be improved in proportion to the increase of the free sulfuric acid beyond thisamount, While keeping with-in the limits of 10% and 15% total acid before mentioned. At higher concentrations the amount of condensed products incapable of use for the manufacture of acetic acid gradually increases with the increase of concentration of the lacid, and with an absorbing solution containing 40 per cent. or more of sulfuric acid it takes only a short time of contact for all the acetic iallddehyde tofbe converted into crotbnic aldey e. i j

I have found that, with whatever concentration of sulfuric acid, the best absorption, with the best yield, always occurs at temperatures -of about 20 to 40 and preferably about 25 or 30 to 40 C.

figure as above mentioned. It is very important to cease the introduction of the aretylene v during the distilling operation, because at a raised temperature the acetylene would render the salts or compounds of mercury inactive much more rapidly, so that the total yield of acetic aldehyde would be reduced. Moreover for the distillations the temperature must not be raised too Infuch (not above about 50-60 C.), because -by 75 raising the ten'iperature to 80 C. for eX- ample, the yield of acetaldehyde is greatly prejudiced. Nevertheless toward the end of the Working, the temperature can be raised to to 100 C. to drive 0H the acetalde- 80 hyde from the liquid as completely as possible.

Toi-king as above described the acetylene can be introduced with the greatest possible rapidity into the absorption liquid, a point which is of very great importance, because the rapid introduction of the acetylene, naturally with complete absorption without eX- cess, also assists in producing, with a certain given weight vof oxid or compound of mercury, the largest multiple of this weight in acetic aldehyde.V For the yield of acetic aldehyde in relation to the weight of oxid or compound of mercury employed'diminishes in proportion to the prolongation of the introduction of the acetylene, since the oxid or compound of mercury used becomes more and more inactive.'

There has always 'been obtained in the process, as herein described, a residue of the mercury compound employed', consisting of a gray or dark gray powder, with a yell-ow-y ish o'r brownish tint, this tint varying-in accordance with the percentage of acid em- The greater part of this powder containing metallic mercury represents a mercury derivative of acetylene, perhaps of high polymerization, which by treatment with any oxidizing agents, say Vby chlorin Ior nitric acid, or by a mixture of hydrochloric 4and nitric acids, or by peroxids in presence ents No. 1684s of 1913, 17017 of 1913, 16957 12o of 1914 and French Patent No. 474246 already referred to, it is proposed to introduce the acetylene in excess, so that the unabsorbed acetylene acts as a vehicle for the acetic aldehyde formed. 125

With the present invention it is essential that only thequantity of acetylene capa-ble of being absorbed shall pass through the reaction liquid; this is to preserve in the salt or compound of mercury the highest power of production of acetic aldehyde in relation to the employed weight of the salt or compound of mercury, as excess of acetylene rapidly renders the salt or compound of mercury inactive.

In the said French Patent No. 474246 lthe excess of acetylene introduced is to replace mechanical agitation. This is impossiblein the present invention, as it is important that agitation shall be employed, while avoiding excess of acetylene.

Further, the quantity of oxid of mercury or salt or compound of mercury contained in the absorption liquid is of essential iinportance for the present invention. I have' found that even if all the other conditions before mentioned (I, III, I V, V and VI),\

are observed, a very poor yleld is obtained on employing large quantities of mercury salt or compound in an absorption liquid, as relatively little acetic aldehyde is formed. For example by employing in an absorption liquid 3 to 4 kilos of sulfate or other compound of mercury to 10 liters of o compound, calculated on the quantity of the absorption liquid is diminished, the other conditions above set out being observed, the quantity of acetic aldehyde produced will increase, but on the other hand the quantity of mercury compound must not be taken too low as the absorbing power would then diminish too much, so that the industrial manufacture would be impossible or prejudiced. I employ not more than about 10% and preferably between about 3% and`6% of mercury compound calculated on the weight of the absorption solution.

The oxid or compound'of mercury employed should be dissolved completely in the absorption liquid before the introduction 'of the acetylene. This would not be possible if an absorption solution were employed containin no free sulfuric acid (i. e. sup o singc yl enough acid to be used to com" me with the oxid of mercury) or only 3 to 5 per cent., and the result would be al relatively poor yield of acetic aldehyde, asin such case the oxid of mercury or the sulfate of mercury does not dissolve or onlydissolves partially in the absorption liquid before the absor tion of the acetylene; for this reason while eepin within the limits'before mentioned, su ciently more acid is necessary in order that the mercurial substance or compound may be dissolved. v i

The reason for this-lies in the fact that in introducing the acetylene into the absorption liquid there is formed after acertain time a precipitate representing. a compound vof acetylene with the mercury body which, in this way, gives the greatest possible surface to. the acetylene introduced, serving as a contact agent, so that the greatest possible absorption is thus insured.

It must not be thought however, that the absorption is immediately intense the moment the acetylene is introduced. For it has been found that during a certain time vthe absorption of the acetylene introduced is very slight, and this may even last for an hour, or up toy several hours or more, according to the composition of the absorption liquid, and only increase after the vollmiinous precipitate produced by the acetylene introduced becomes more and more dark, or rather grayish-black, reaching the maximum absorbing power then. It is onlyv then that the real contact substance begins to 'loA produce its effects, as shown by the fact that the acetylene can be introduced abundantly at the same time being absorbed whereas before this state of color of the mercurial precipitate is reachedonly a very weak current of acetylene can be introduced and absorbed 'as otherwise the `acetylene passes through without entering into react-ion.

Based on these observations it is believed that it is carbid of a lower o'xid or oxids of mercury which is formed and serves as a contact substance, since it has been found that on passing acetylene through a liquid containing mercurous sulfate, the v same black or black-gray precipitate is formed having the same properties as the product obtained after the introduction of the acetyleneduring a relatively long time into a so- -lution containing a mercurio salt.

Proposal has heretofore been made to con.

- vert the acetylene first into acetaldehyde and to convert this latter into acetic acid, all in one operation, by introducing a mixture of acetylene and an oxidizing gas, into a S0111'- tion -containing a mercury compound. The failure of such process, I beheve, 1s caused by the fact that the first reaction referred to i requires, as a catalyst, a mercurous com pound, and 'by the introduction of the 0x1- dizing gas the formation of this black or grayish-black precipitate, capable of eectively acting as the catalyst, was prevented. It will be seen that the formation of.` acetaldehyde according to thisprocess requires reducing conditions whereas the formation of -acetic acid therefrom requires oxidizing conditions. A A

Considering only the fact that in proportion as acetic acid is formed the concentration of the acid would increase more and more, the result in such rocesses would further be a-disturbance o the equilibrium in the conditions necessarytoarrive at the in-.

- 'dustrial result above indicated. The conditions necessary in my present invention are therefore also in contradiction with a process recently proposed infwhich one oxidizes simultaneously or employs an cxidizer such.

as ferrie-sulfate to prevent the reduction of the salt of mercury.

Further it has been found that the acetylene introduced should be purified, before its introduction, from impurities such assul fureted and phosphoreted hydrogen, am-

(b). Apparatus employed for the mamefactureof acetic aZdeLg/de.

Glass is of course inapplicable for apparatus on'an industrial scale, and in view of the volatile nature of acetic aldehyde it is dificultto employ earthenware alone, the more so as strong agitation is necessary and an apparatus capable of standing pressure and heating is also necessary.

An ordinary earthenware apparatus is unsuitable for the conditions required, especially as there is risk of its breaking, and

acetic aldehyde and acetylene are very volatile and inflammable.

Iron resists. amalgamation, but it is attacked by acids, andin dissolving it precipitates mercury even before the conversion of acetylene into acetaldehyde begins.

I have devised a way of overcoming thesedifiiculties, making it possible to employ iron apparatus, thus rendering the appara` tus safe in working, especially guarding against the danger arising from the presence of acetic aldehydeand acetylene. This will now be explained.

Based on the property possessed bylead of easily withstanding the action of sulfuric acid-in 'which lead does not dissolve but Vrather forms a layer of lead sulfate-l 'have found that by treating or heating the lead, for example ina lead-covered iron apparatus, with, more or less diluted sulfuric acid,

' preferably in presence of an oxidizing agent such as nitric acid, there is formed a layer of sulfate of lead, and (especially in pres-` ence of an oxidizing agent such -as nitric acid) oxid of lead mixed with sulfate 'of lead-which remains attached toV the lead and which, even if the, metallic mercury comes in contact with' it, gives no amalgamation,- as this layer of sulfate of lead protects the lead against amalgamation and does not dissolve in the absorbing liquid.

In practice for example a cylindrical iron apparatus of any capacity, for example 1000 to 5000 liters, is constructed,'having its inside covered with lead, the surface of which is treated in the manner referred to, so that thelayer above indicated is obtained on the lead. Likewise the stirrer provided is covered with lead coated with this layer. impenetrable to 'the mercury.

As a measure of precaution the cover may also be similarly coated, with the exception of the shaft of the stirrer where it passes through the stuiiing box, which should be very tight to prevent leakage of the vapor of the acetic aldeliyde. 4

Moreover'the apparatus may be provided, for heating, with a double bottom, or it may simply be provided with a tank or bath in which Water can be heated to boiling, or, though with less advantage, there may be introduced into the interior of the apparatus,` pipes of lead or iron pipes covered with lead on which the layer impenetrable to mercury is produced.

The employment of apparatus having parts made of lead and coated with an insoluble layer containing lead sulfate, as described herein, for carrying out the process of making acetaldehyde by passing acetylene into the herein described absorbing solution, lforms the subject matter of a divisional application 229,174, filed April 17, 1918. l

Less advantageously, one could use apparatus made of iron lined with stone slabs, or apparatus made of earthenware or the like, and employ therein heating or cooling pipes made of or -covered with lead provided with the described layer impenetrable to amalgamation.

E'ample.

- vessel being provided with stirrer arms a a mounted on a shaft b and adapted to be rotated very rapidly by the beveled gears, c c' from the'driving shaft al provided with fast and loose pulleys e e. f indicates an agitating fand spouting member likewise f and spouting nozzles C2 as known for assisting the agitation lo the liquid conatv Vfixed to the shaft b and provided with slots ,outside surface of, the stuiling box g, the

shaft b upto the point Where'it passes into the stuffing-box, arms a, and the .interior and exterior surfaces of the agitating member f, and of the inlet pipe 'y'. y

1I indicates a pump for supplying the acetylene gas to vessel A by a lead pipe y' controlled by valve j. Z indicates the outlet pipe from vessel A,`said pipe being controlled bya valve Z and depending into a in which theV absorption vessel A is mounted, and serving for heating" and vcooling the ,25

to a epth of about 2 to 4 meters. m is a relief valvefor the chamber m. n indicates' the discharge valve of vessel A.'

` B indicates an outer jacket or container vessel A by means respectively of a steam inlet pipe p and drain pipe .12', and of a water inlet pipe q and water overflow pipe g. p2 p3' indicate the controlling valves of pipes .p p and g2 g3 the controlling valves of pipes g g respectively.

.In order to form the amalgamation-re -sisting layeron therequired parts, the leadlined interior -of the apparatus and the lead-faced parts to. be protected are rs't treated with a mixture of dilute sulfuric acid containing nitric acid, andare heated v until a layer of lead sulfate has formed on thelead so that the metallic lead will 'not be in contact with 4the absorption liquid whenthis is introduced. v After the ycoating operation the acid liquorl is run oi.

-The apparatus thusfprepared is charged with a mixture of 850 kilos .of water and 150 kilos of concentrated sulfuric acid (96-4 90% strength) to which are added 40 to 50 k11os of oxid of mercury; the whole is heati `ed to about 80 tof100 C., until complete solution has taken place, aand after cooling, at a temperature of about 35 to 40 C., acetylene is introduced, being drawn by the pump' z' Yand forced into the absorption liq- Z from the absorption vessel is led, s6 thatv uid under a superatmospheric pressure of say about atmosphere, care being taken, as before explained, to provide atthe outlet side of the absorption vessel A the back pressure ofa liquid column of about 2 to 4 meters height in back'pressure chamber m, into the bottom of-whichthe outlet pipe the pressure of this height of liquid is exerted at the outlet side.

At the commencement of the operation care iis taken that the acetylene shall. not

pass too rapidly. During this time the 'white' precipitate which is formed vby the introback (pressure chamber m containing liquid,

duction of the acetylene darkens, becomes darker and darker, and at length black or graysh black.

The liquid now possesses -sorbing power for the acetylene.

From this moment the acetylene is in troduced as much and as rapidly as possible,

Apreferably by several pipes "leading the acetthe greatest abl duction of the acetylene, the temperature is raised gradually from about 50-60 C., to distilof the acetic aldehyde through the pipes leading to a condenser (the valves being opened' and the valve Z- closed during this operation). To avoid anyloss this condenser is cooled by the brine of an ice machine, and the acetic aldehyde escaping condensation in the first` condenser is led to a Vsecond vessel cooled by the brine of an ice machine. A This receptacle for collecting the acetic aldehyde is vfurther provided with a reflux condenser lalso vcooled by the brine 'of an ice machine, to make sure that no loss shall occur.-

After distilling olf the greater part ofthe aldehyde, the temperature is lowered again to 35 to 40. C., and the introduction cf the acetylene is then recommenced, and so on. These operations are repeated alternately until the absorbing power of the absorption liquid diminishes greatly or ceases, and then for'nishing, (the introduction of acetylene being stopped) the liquid is heatedl to a temperature of A to 100 C. to distil off the last traces of the acetic aldehyde.

this wayafter about 20 to 25 hours, more Aor less, of introduction of acetylene, accordv 'ing to the particular case, about 500 to 7 00 kilos of acetic aldehyde can be obtained with a yield of90 to 95- per cent. or more,'calcu lated on the weight of the acetylene intro- V duced. i

The residue formed is converted into oxid of mercuryfor reuse. As illustrating what Awould be the effect ofmaking changes in ther conditionso'fthe process above set out, and outside' the invention, the following` may be mentioned n ,If in the foregoing example, instead `of 15%v of sulfuric acid, vthere taken say `more than 20% the yield of acetic aldehyde would be much smaller, and even the yield of acetic aldehyde relatively to the quantity of acetylene introduced would diminish considerably, as an appreciable portion of the f aldehyde would beconverted into resinous products, 4and at the same time the absorbing power'of the contact substance, that is to say thexmercury compound contained in ,only be possible to introduce a restricted the absorption liquid would' diminish. If

on the other hand the quantity of sulfuric acid were reduced, for example to 4 to 5 per cent., the yield would diminish very considerably, so that only about 100 to 200 kilos of acetic aldehyde would be obtained.

Again if in the above example the duration of the introduction of the same quantity of acetylene were prolonged (i. e. if the acetylene were introduced slowly), the yield of ace-tic aldehyde would be much lower, and toward the end it would not be possible to introduce all the acetylene, since it would no longer be absorbed, as the contact substance would have become inactive.

If in the example '60 to 80 C. were chosen as the temperature for introducing the acetylene, a total yield of about only 100 to 150 kilos of acetic aldehyde would be obtained, with a considerable quantity of resinied products, and moreover it -would quantity of acetylene, as the original quantity of acetylene of the above example would no longer be absorbed, even if the time were doubled for example to sa 40 to 50 hours. This diminution of yield ecoines progressively more pronounced ashigher temperathe yield would diminish considerably and tures are used.

Again if in the foregoing example after the introduction of the acetylene at the temperature therein indicated, there were chosen for the distillation a higher temperature than 50 to 60, that is to say if the temperature is raised directly to 80-100 C.,

it would no longer be possible to introduce the same quantity of acetylene as if the conditions of the example above given liad been followed.

If in the example the acetylene were introduced in excess, so that the acetic aldehyde was .carried away with it, this would involve on theA one hand the loss of the acetylene together with its complicated recuperation, and on the other hand the yield of ae'tic aldehyde would be much less, as

v ing solution, while maintaining the temperature at not above l40, C. during the introduction ofA the acetylene, the acetylene being introduced in a weaker current at the beginning, until the mercury compound in Whereafter the acetylene is introduced asl rapidly as possible, while avoidingrv excess and non-absorption, strong agitation being maintained during the introduction of' the acetylene, the acetaldehyde formed being distilled off at required intervals by raising the temperature to not above 50 to 60 C., while interrupting the introduction of acetylene, and the temperature being thereafter again reduced to not above 40 C., for the reintroduction of the acetylene.

2. In a process for the manufacture of acetaldehyde, the improvement which comprises passing acetylene into an absorbing solution containing sulfuric acid in amount between about 10% and about 15% total acid, and a mercury, compound in amount corresponding to between 3 and 6 per cent. of metallic mercury, both calculated on the weight of the absorbing solution, while maintaining the temperature between 25 and 40 C. during the introduction of the acetylene, the acetylene being introduced in a weaker current at the beginning, until the mercury compound' in the solution has become gray to grayish-black, indicating that the solution has about attained its maximum absorbing power, whereafter the acetylene is introduced as rapidly as possible, while avoiding excess and non-absorption, maintaining strong agitation during the introduction of the acetylene, distiliing oli' the acetaldehyde formed at required intervals by raising the temperature to not above 50 to 60 C. while discontinuing the introduction of acetylene, reducing the temperature to not above 40 C. for the reintroduction of the acetylene. u

3; In a process for the manufacture of acetaldehyde, passing acetylene into an absorbing solutionl containing about 10% to about 15% of total sulfuric acid, and s ulfate of mercury in amount correspondlng to between 1 and 10 per cent, .of metallic mercury, lboth calculated on the weight of the absorbing solution, while maintaining the temperature between 25 and 40 C. during the introduction of the acetylene, 1ntroducing the acetylene'as a slow current at the beginning, until the mercury compound in the solution has become gray to gray1shblack, indicating that the solution nas about attained'its maximum absorbing power, and thereafter introducing the acetylene as rapidly as possible while avoiding excess and non-absorption, maintaining a strong agita-v tion during the introduction of the acetylene,

`and as soon as the acetylene ceases to be quickly absorbed, discontinuing the introduction of acetylene, and distilliug oil' the acetaldehyde formed, by ralsing the temperature to not above 50D to 60 C, and

thereafter again reducing 'the temperature to between 25 and 40 C., and again rapidly .leading in acetylene, and repeating the cycle of operations of distilling off aldehyde and rapidly introducing acetylene, and finally heating the liquid to about 80-100 C., for completely removing the acetaldehyde therefrom.

4. In a process for the manufacture of acetaldehyde, passing acetylene under a slightly increased pressure of about h alf' an atmosphere into an absorbingv solutionv v containing sulfuric acid in amount not more than about 15% and not less than about 10 per cent. total acid, and a compound of mercury in amount corresponding to between 1 and 10 per cent. of metallic mercury both calculated on the weight of the.absorbing solution, 'while maintaining the temperature between and 40 C. during the introduction of the acetylene, the acetylene being introduced in a weaker current at the beginning, until the mercury compound in the solution. has become gray to grayishvto - forth.

black, indicating that the solution has about attained its maximum absorbing power, whereafter the acetylene under said slightly Iincreased pressure is introduced as rapidly as possible while avoiding excess'an`d nonabsorption, strong agitation being maintained during the introduction of the acetylene, the acetaldehyde formed being distilled off at required intervals `by raising the temperature to not above 50 C. to 60 C. and while interrupting the introduction of acetylene and the temperature being reduced to not above 40 C. for the reintroduction of the acetylene, substantially as set 5. In a process for the manufacture of acetaldehyde ypassing acetylene under a slightly increased pressure of about half an atmosphere into an absorbing solution containing sulfuric acid in amount .not more than about 15 per cent. -and notl less than about 10 per cent. total acid, and a compound of mercury in amount corresponding to between 3 and 6 per cent. of metallic mercury, calculated on the weight of the absorbing solution, while maintaining the temperature between 25 and 40 C. during 'the introduction of the acetylene, the

acetylenebeing introduced in a weaker current at the beginning, until the mercury compound in the'solution has become gray to grayish black, indicating that the solution .has about attained its maximum absorbing power, whereafter the acetylene vis introduced as rapidly as possible, while avoiding excess and non-absorption, strong agitation being maintained during the 1ntroduction of the acetylene, the acetaldehyde formed being distilled off at required intervals by raising the temperature to. not above 50 to 60 C. while interrupting the introduc tion of acetylene and the temperature being reduced to not above 40 C. for the reintroduction of the acetylene, substantially as set forth.

6. In a process for the manufacture of acetaldehyde, passing acetylene deprived of impurities such as sulfureted and phosphereted hydrogen and ammonia, intoV an absorbing solution containing sulfuric acid in amount not more than about 15 per cent. and not less than about 10 per cent. total acid, and sulfate of mercury in amount coracetaldehyde, the improvement which comprises the step of first preparing an absorbing -solution containing sulfuric acid in amount not more that about 15 per cent. and not less than about 10 per cent. total acid, and a mercury compound capable of reacting with sulfuric acid to form mercuric sulfate, such mercury compound being present in amount corresponding to 1 to 10 per cent. of metallic mercury calculated on the weight of the absorbing solution, by heating an aqueous liquid containing said proportion of sulfuric acid and such mercury compound until the mercury compound is dissolved, and thereafter passing acetylene into the absorbing solution while maintaining the temperature at not above 40 C., the acetylene being introduced in'a weaker current at the beginning, until the mercury 'compound in the solution has become gray to grayish black, indicating that the solution has about attained its maximum absorbing power, after which the acetylene is introduced as rapidly as possible, while avoiding the introduction of acetylene more rapidlyfthan the same can'be absorbed, and until the activity ofthe. solution for the 'absorption'of acetylene decreases, and then discontinuing the introduction of acetylene.

8. In a process for the manufacture of acetaldehyde, the improved method of preparing an absorbing solutioncontaining sulfuric acid in amount not more than about 15 per cent. and not less than about 10 per cent. total acid, and .a mercury compound capable of combining with such acid to form mercuric Sulfate, such compoundbeing used 6 per cent. of metallic mercury, calculated Y on the Weight of the. absorbing solution, by

heating an aqueous liquid containing Suid proportlon of sulfurlc acld und lof such mercury compounduntil the mercury com@ r pound is dissolved, and thereafter slowly passing acetylene into the absorbing solu- 1 tion while the temperature thereof is main- 10- tained at not above 40 C., until the mercury compound in the solution has become vgray to grayish black. 1

Inwitnese whereof I-have hereunto signed my nume in the presence of"tWo subscribing -witnesses. HENRY DREYFUS.

` Witnesses THOMAS LAING WHITEHEAD, ROBERT MILTON SPEARPOINT. 

